The invention in general relates to a method of skiving shallow grooves in metal. In particular, the invention relates to the continuous installation of metal ribbon, e,g., precious metals such as gold, palladium, and silver alloys into grooves cut in flat metal strip, which is thereafter rolled and fabricated for various end uses including the manufacture of precious metal electrical contacts and connectors. In a prior art method a flat metal strip, typicaly 0.14 inches thick and several inches wide, is fed into an apparatus which skives (cuts) grooves of about 0.025 inches in depth. A thin precious metal ribbon of a thickness equaling the depth of the groove is forced into the groove and bonded by high pressure rolling. Since the strip is thereafter rolled several times to reduce its thickness, it will be clear that the depth of a groove must be at least the thickness of the precious metal ribbon placed into it. If the ribbon protrudes above the surface of the strip before rolling, it is squeezed over the face of the strip during the rolling process, becoming excessive in width and insufficient in thickness and thus becoming waste which must be recovered and recycled at significant cost to the manufacturing process. The normal variation in thickness of such thin base metal strip is approximately .+-. 1 1/2%. If the depth of the groove is too shallow by an amount equal to the maximum variation, about 15-16% of the precious metal is exposed after assembly and becomes waste. It will be readily appreciated that such a waste problem is expensive and highly undesirable since the precious metal is costly and must be recovered. If the groove is skived too deeply, no precious metal waste is created but the strip after rolling contains a larger proportion of the precious metal inlay than is necessary, which results in a more expensive product than if the groove had been skived to the correct depth.
In the present method of skiving grooves in the base metal strip, the cutters are adjusted to the average desired depth. Unfortunately, owing to the variations in thickness of the base metal stock the groove is often too deep or too shallow. The present invention overcomes this problem providing a method and apparatus of skiving one or more grooves in base metal strip stock which are of predetermined and constant depth, regardless of variation in the strip stock thickness.
Similar strip contacts are shown in U.S. Pat. No. 3,535,781 to Comey, Jr. and U.S. Pat. No. 3,468,015 to Santala, both of which are concerned with the problem of diffusion of the precious metal into the base metal stock and not with the skiving of grooves and the conservation of precious metal, which is the problem solved by the present invention.
U.S. Pat. No. 2,961,762 to Clark contains a description of a process similar to that to which the present invention is applied. In particular, Clark is concerned with the formation of arcuate precious metal ribbon in order to improve the bonding and does not concern himself with controlling the depth of the groove which receives the ribbon.
Reeve, in U.S. Pat. No. 2,226,944, discusses another aspect of the process with which the present apparatus of the invention is used. In order to obtain bonding without application of adhesives, it is necessary for exceptionally clean surfaces to be prepared. The surface of the base metal strip is cleaned by the skiving immediately prior to introduction of the precious metal ribbon into the groove. The precious metal ribbon is cleaned and kept free of contamination by heating in a hydrogen or inert atmosphere immediately prior to its application to the precious metal strip.